This invention relates to a method of minutely roughening a surface of a substrate by etching the substrate surface such that the etched surface is scattered with numerous microscopic islet-like land regions which are unetched regions. To provide the islet-like land regions the substrate surface is scattered with microscopic droplets of a masking material in advance of the etching operation.
Often it is desired to minutely roughen a smooth surface of a substrate. In many cases the purpose of roughening a substrate surface is to enhance the adhesion of a paint film or a functional coating film to the substrate surface, and in some cases the purpose is to prevent sticking of a certain article to the substrate surface such as, for example, sticking of a magnetic head to a magnetic disk surface or sticking of a paper sheet to a glass plate used in a copying machine.
One of possible methods for minutely roughening a substrate surface is etching the substrate surface with suitable masking. Particularly in the case of a glass or ceramic substrate it is desirable that minute roughening of the surface could be accomplished by an etching method.
It is a well known technique to form a relief pattern on a glass substrate by masking the substrate surface in the areas of the aimed relief pattern with an erosion resistant synthetic resin or rubber and then etching the exposed areas of the substrate surface with a suitable etching agent such as hydrofluoric acid. The masking is made by screen-printing or photolithography. However, in the case of minutely roughening a substrate surface it is necessary to leave the surface unetched in numerous dot-like regions each of which is only tens of micrometers or smaller in diameter, and it is very difficult to mask such dot-like regions by a conventional method.